Chromogramin A (CgA) is a high MW protein that is found in essentially all human endocrine tissue. It is co-secreted with the specific hormone form each tissue in both its normal and malignant state. Because it is secreted in excess by endocrine tumors, CgA is an emerging serum marker for endocrine cancers. However, very little is known about the regulation of CgA synthesis and secretion and consequently no provocative about the regulation of CgA synthesis an descretion and consequently no provocative tests for it have been developed. We propose to study the biosynthesis and secretion of CgA and compare it to that of one of its associated hormones, calitonin (CT), in cells that produce both substances. This will be accomplished in cell lines established in our laboratory that are representative of three types of endocrine cancer. One cell line is derived form thyroidal C-cells (medullary thyroid carcinoma) and thus produces CgA and CT eutopically. The other cell lines are derived from lung tumors and thus produce CgA and CT ectopically, one from a classical and one from a variant small cell carcinoma of the lung. We shall study the regulation and the co-regulation of the secretion of CgA and CT by these cells in culture. The secretagogues to be studied include minerals, neuroendocrine mediators, and peptide hormones. The role of "second messengers" will be evaluated by testing the effects of forskolin, phorbol esters, and ionophores. Secretion of CgA and CT will be evaluated by radiommunoassays for the two substances which have been developed in our laboratories. The regulation of the bio-synthesis and transcription of CgA will also be studied. This will be accomplished by pulse- chase labeling experiments and through the use of cDNA probes developed in our laboratory to quantitate CgA-specific mRNAs. These probes will thus be applied to regulatory studies of the molecular biology of CgA using recombinant DNA procedures. This information about CgA regulation will facilitate our clinical goal which is to develop provocative tests for CgA and thus refine the use of the measurement of serum levels of CgA as a tumor marker in the diagnosis and management of patients with the large number of endocrine tumors. The RIA will be applied to studies of patients with the large number of endocrine tumors, including neuroendocrine lung cancer, for which CgA is a potential serum marker. These basic and clinical studies should help us to elucidate the fundamental and clinical significance of CgA in endocrine cancer.